One of the things you need to know is the visa that he would be going on?
If he's moving within the same company, he will be on a L visa, and that would give you the opportunity of applying for a work authorisation once you get there if you wanted it. The L visa is a relatively simple process, and the company's immigration lawyer should take care of most of the details.
The relocation expenses will be paid by the company, and they will be allocated to the receiving organisation rather your home organisation, so DH's boss can only put up so much of a fight.
On the money front, there are two things to look at - the actual relocation and repatriation, and the money you get while you are there (expatriate vs local basis).
For the relocation, you should of course get packing and shipping costs, flights and a couple of weeks of full business expenses, the services of a relocation consulatant. A bonus is if you can get a lump sum for getting your house in order (eg replacing small electricals, buying curtains etc.) and an interest free loan for cars, major appliances, TV etc., and a guaranteed resale value. They should also do your US and UK taxes for the years of your relocation and repatriation. It would be good to get a holiday allowance in your first year, allowing you to return to the UK to settle your affairs.
For ongoing salary - UK salary and holidays is good plus your UK child benefit amount, but a bonus is a paying for one of your houses. When we were expat, the company paid for our rental house, and we paid for our UK house. When our house was rented, we had to make a contribution to our rental, minus our agent fees. They paid an amount for our utility bills. We also got money to cover a trip back to the UK each year.